Let me start by saying I am a noob at repairing PCB's , and I am having trouble finding a resource that will allow me to visually identify components. I am hoping someone will know what the component is. I believe it is a surface mount transistor , but I am not sure.

https://imgur.com/a/dhuEiyj

 

That C15 is a ceramic capacitor. Different values of SMD caps are having the same size, so youre not going to guess its value unless you do some circuit tracing. Where do both ends of the cap. go?



Allen

 

Thanks so much for the reply .. does the color of the component say anything about its value. It is just that on some circuit boards i have noticed that devices that look similar are black. I will take it out of its housing tomorrow and take a pick so we can try and determine where the wire goes. Thanks again.

 

 

So i tried to trace this out , if you look at the light blue line i traced it appears it passes through and circles around pin 7 on the chip and back out . If you notice the solder point on the back view in the dead center i have labeled with a ?, not sure what that is. Looks like C13 goes directly to pin 3. I have included a pic of the back of the board , it appears some traces go to different pins for sure. Just an observation here , is that many of these look exactly the same , like c12 and c13 look the came as c15. Is it possible they could be the same value ? I know that does not really mean anything , just wondering. I hope this helps us ( I know this isn't the correct pin out for the chip , i just labeled them for reference so you could see where you are on the back view.)

 

About the only thing that can be said of the capacitor is that it isn't a C0G type, which usually are moderately precise values and have nearly zero temperature coefficient of capacitance. C0G types are usually nearly white. The yellowish ones can be a wide range of values in several different types (all ceramic, but different characteristics). It might be the same value as those nearby that appear to have similar circuitry to the connector, but it really is a guessing game. If the thickness is different, the value will be different, but that is all that can be said with any reasonable certainty.

The point marked with a question mark is to a "ground plane" - circuit "common"

 

Just noticed your pin numbering on the bottom view is wrong. In integrated circuits, with a very few weird exceptions, pins are numbered consecutively going counterclockwise from pin 1, as viewed from the top. So, an 8-pin dual In-line package (DIP in North America, DIL in the UK; Chinese vendors on ebay tend to call anything that has through-hole pins DIP) is pins 1-4 down one side, the 5-8 up the other - pin 8 is opposite pin 1.

You have to be careful if pins are "missing" as sometimes happens where a pin is omitted to make a wider gap if high voltage is involved. Usually the omitted pin position is numbered as if there were a pin there, but not always. Not many ICs are made with omitted pins but they aren't really rare, either.

To elaborate on the photo of the back:
The brighter green is solder mask (prevents solder from "sticking" to copper) over copper foil. The more bluish area around the tracks on pins 7 & 8 is where copper has been etched away and the bare substrate is covered with solder mask. The pad marked with a question mark is a "via" - its sole purpose is to connect from one side of the board to the other, in this case to the large copper area. Usually the clearance between pads and tracks and the copper plane is about equal. For some reason this board has been made with much greater clearance for the tracks than for the pads. Vias into the plane often have no clearance or visible pads - just holes. Note that the via and pin 4 of the IC have at least two narrow "spokes" of copper (again, brighter green) connecting the pad to the plane. This is a "thermal relief" connection - electrical connection is made but by etching away some copper the heat conduction to the large copper are is reduced. This is very helpful if you need to remove parts or are soldering them in by hand. The copper plane can take away heat very quickly and make soldering or desoldering a good deal more difficult.

It has become fashionable with hobbyist circuit boards to use black solder mask. I dislike it because it makes trying to trace a circuit, especially in a photo, difficult.

 

DIP chip packages are numbered like this:

 

Thank you so much for the reply , this has all been very helpful information. I new the pin numbering was probably wrong , i just did it for point of reference for Allen above to be able to reference location for the back side of the board he had asked be for a picture of. But thanks for the images , i will try and be more accurate on detailing these things in the future.

Lets say i wanted to try and figure out what the value of one of the capacitors is in the near by circuitry , what would be the best way to do this .. and then again , where would a guy purchase these ? It seems after doing more research these are non polarized capacitors ? Does that sound right ? I saw a video of a guy checking each side of one on a circuit board to determine what he was referring to as a high and a low value.. if i could determine the value of one near by , i think i would just try and buy some and give it a go. If they are not too expensive ..

 

Sorry for the late reply as my daughter was visiting me for the last few days.

I was expecting the under side of the PCB for that 2 particular points were going to some places near to the two chips, so we can guess the values of the Caps from the datasheet of the IC. But it looked like the underneath of the PCB are quite monotoneous, mainly covered by Ground.

I ordered my SMD capacitors from eBay and there are about a hundred values each strip containing 20 caps. I laid them out on the table and found they are all the same size regardless of their values. 104 (100nF) looks exactly the same as 182 (1.8nF) and there was no markings on them.

At least the resistors have 3 digits marking on them so we can know its resistances from the numbers.


To measure the capacitance you'd need a capacitor meter or an ESR meter. Some multi-meters also include this function and my meter can even measure frequencies in the audio range.

This is the ESR meter I bought from Banggood and I assembled it myself. Some fancy ones use GLCD just to attract more buyers.


If you are able to remove one of the caps from your PCB, you can measure its value using the multimeter I mentioned or buy a cheap ESR in kits form.

A lot of the cap are bypass capacitors of values 100nF. It you think you're lucky.... (forget what I said).

You need a hot air work station to remove the capacitor. If you watch utubes, you may find that there are other ways to remove an SMD component. But whatever you do, try it out on a junk board first before you do the real thing.

Allen

 

Just a thought....

Did you measure the burned cap with an ohmmeter ? If it was shorted, just remove it and try out the board again. If it was a decoupling cap (usually 100nF), then the board might work without it.

Allen

 

Thanks Allen , its taken me a while , but i have always wanted to get myself a little lab up and running. I have a hot air station i found on spark fun , and it is awesome. I have the shorted one removed , but i also remove one that looks identical right beside of it , and indeed it is 100nf (actually measured 105.2) on my ESR that i got . I did not come back and read this until just now , so , i have not tried the board again to see if it will work with out it , but like i said now i have two of them out. I will just go ahead and replace them. My question is , at what volatage to these things typically operate at ? some of the ones i have seen say 100nf 50v .. but on a site called digikey , they list it as a .1uf 6.3v .. would you happen to have the link to the ebay where you ordered those ? I really appreciate all the advice and help. I am going to feel quite accomplished if i can get this right I am just going to take my time and be maticulous .. hopefully it works out .

 

is this what i am looking for ? though.. some of these numbers i dont quite understand
https://www.ebay.com/itm/100pcs-080...epid=2255388119&hash=item3ab3ec7b0b:rk:4:pf:0

 

This is the one that threw me off a bit .. https://www.digikey.com/product-det...15D/490-10390-1-ND/5026263/?itemSeq=282679328